Ammonia blood test
Serum ammonia; Encephalopathy - ammonia; Cirrhosis - ammonia; Liver failure - ammoniaThe ammonia test measures the level of ammonia in a blood sample.
How the Test is Performed
A blood sample is needed.
Blood sample
Venipuncture is the collection of blood from a vein. It is most often done for laboratory testing.
How to Prepare for the Test
Your health care provider may ask you to stop taking certain drugs that may affect test results. These include:
- Alcohol
- Acetazolamide
- Barbiturates
- Diuretics
- Narcotics
- Valproic acid
You should not smoke before your blood is drawn.
How the Test will Feel
When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise. This soon goes away.
Why the Test is Performed
Ammonia (NH3) is produced by cells throughout the body, especially the intestines, liver, and kidneys. Most of the ammonia produced in the body is used by the liver to produce urea. Urea is also a waste product, but it is much less toxic than ammonia. Ammonia is especially toxic to the brain. It can cause confusion, low energy, and sometimes coma.
This test may be done if you have, or your provider thinks you have, a condition that may cause a toxic buildup of ammonia. It is most commonly used to diagnose and monitor hepatic encephalopathy, a severe liver disease.
Hepatic encephalopathy
Loss of brain function occurs when the liver is unable to remove toxins from the blood. This is called hepatic encephalopathy (HE). This problem ma...
Normal Results
The normal range is 15 to 45 µ/dL (11 to 32 µmol/L).
Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or may test different samples. Talk to your provider about the meaning of your specific test results.
What Abnormal Results Mean
Abnormal results may mean you have increased ammonia levels in your blood. This may be due to any of the following:
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Gastrointestinal (GI) bleeding, usually in the upper GI tract
Gastrointestinal (GI) bleeding
Gastrointestinal (GI) bleeding refers to any bleeding that starts in the gastrointestinal tract. Bleeding may come from any site along the GI tract, ...
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- High body temperature (hyperthermia)
- Kidney disease
- Liver failure
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Low blood potassium level (in people with liver disease)
Low blood potassium level
Low blood potassium level is a condition in which the amount of potassium in the blood is lower than normal. The medical name of this condition is h...
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- Reye syndrome
- Salicylate poisoning
- Severe muscle exertion
- Ureterosigmoidostomy (a procedure to reconstruct the urinary tract in certain illnesses)
- Urinary tract infection with a bacteria called Proteus mirabilis
A high-protein diet can also raise the blood ammonia level.
Risks
There is little risk in having your blood taken. Veins and arteries vary in size from one person to another and from one side of the body to the other. Taking blood from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight, but may include:
- Excessive bleeding
- Fainting or feeling lightheaded
- Multiple punctures to locate veins
- Hematoma (blood accumulating under the skin)
- Infection (a slight risk any time the skin is broken)
References
Daniels L, Khalili M, Goldstein E, Bluth MH, Bowne WB, Pincus MR. Evaluation of liver function. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Philadelphia, PA: Elsevier; 2022:chap 22.
Mehta SS, Fallon MB. Hepatic encephalopathy, hepatorenal syndrome, hepatopulmonary syndrome, and other systemic complications of liver disease. In: Feldman M, Friedman LS, Brandt LJ, eds. Sleisenger and Fordtran's Gastrointestinal and Liver Disease: Pathophysiology/Diagnosis/Management. 11th ed. Philadelphia, PA: Elsevier; 2021:chap 94.
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Blood test - illustration
Blood is drawn from a vein (venipuncture), usually from the inside of the elbow or the back of the hand. A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. Preparation may vary depending on the specific test.
Blood test
illustration
-
Blood test - illustration
Blood is drawn from a vein (venipuncture), usually from the inside of the elbow or the back of the hand. A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. Preparation may vary depending on the specific test.
Blood test
illustration
Review Date: 2/28/2023
Reviewed By: Jacob Berman, MD, MPH, Clinical Assistant Professor of Medicine, Division of General Internal Medicine, University of Washington School of Medicine, Seattle, WA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
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